The new HSPA+42 network requires a software upgrade to the HSPA+21 network.

T-Mobile officials have repeatedly said that its HSPA+42 network speed is roughly on par with the WiMax 4G networks offered nationwide by Sprint, and the Verizon Wireless LTE networks.

Verizon announced earlier this week that it is adding 19 cities to its LTE network, bringing the total to 74 cities. Verizon launched the LTE network late last year.

Meanwhile, AT&T plans to launch an LTE 4G network in five cities this summer, even as it moves ahead with plans to purchase T-Mobile for $39 billion. AT&T has said that buying T-Mobile will expand its national wireless coverage footprint, which would initially include the areas served by HSPA+42.

Widespread wireless coverage that gives customers data access most anywhere is becoming a way for major carriers to distinguishing themselves, especially as nearly all the major carriers claim to offer roughly up to 10 Mbps data downlink speeds.

The 47 new HSPA+42 cities on T-Mobile include Albuquerque, N.M., Cleveland and Columbus, Ohio, Sacramento and San Diego, Calif., Salt Lake City, and San Antonio. A full list is included in the formal T-Mobile announcement.

T-Mobile pegged its 10Mbps average download speed on HSPA+42 to its T-Mobile Rocket 3.0 laptop modem. The company said that the device has so far seen peak speeds of 27 Mbps, The theoretical throughput is 42Mbps, which is how HSPA+42 got its name.

T-Mobile also calls its HSPA+21 network a 4G network (although theoretical speeds are half that of the HSPA+42 network).

The company lists more than a dozen 4G devices, including six smartphones such as the Galaxy S 4G and a seventh that is upcoming, the BlackBerry Bold 9900, in its product portfolio. T-Mobile has the Dell Streak 7 and the LG G-Slate with Google 4G tablet devices.